[dm-devel] Newbie questions

Alec Thomas lists at swapoff.org
Fri Nov 28 08:10:03 UTC 2003


Hello,

I have a couple of questions about device-mapper. I've had a look at the
source and could not see an obvious answer.

Firstly, is it possible to utilize one device-mapper module from another
without redirecting to the actual device? For example, if I create a new
device-mapper module that maps blocks over the network and I want to
layer dm-crypt on top, am I forced to first map my device, then map
dm-crypt to this device. It would be extremely convenient to be able to
"layer" them without this requirement, so I could effectively call
dm-crypt to do mapping directly from my module.

My second question is somewhat related. I am thinking about doing a
network based block device running on device mapper. What is the "best"
way of communicating with user-space from a device-mapper module? I
would like to do most of the network stuff in user-space to take
advantage of existing cluster communication infrastructure, so it would
need to be fairly high-speed for transfer of blocks to/from user-space.

So, to summarize in a less rambling way :)...

Can device-mapper modules "chain" together without bouncing back through
device nodes?

What is the "best" way of communicating at high volume with user-space
from a device-mapper module?

Regards,
Alec

-- 
Evolution: Taking care of those too stupid to take care of themselves.




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